[MicroBenchmarks,LoopInterleaving] Check performance impact of Loop Interleaving Count with varying loop iterations.

[nilanjana_basu]

Summary

This microbenchmark attempts to find the right loop iteration count threshold for deciding whether to interleave a loop or not for different types of loops, for example, loops with or without reduction inside it, loops with or without vectorization inside it.
Note: Interleaving count of 1 means interleaving is disabled.

[nilanjana_basu]

Added tests for loops with reductions in them.

[nilanjana_basu]

nitpick

[nilanjana_basu]

Added microbenchmark for loop interleaving when vectorization width is 1

[nilanjana_basu]

nitpick on function names, updated comments

[nilanjana_basu]

nitpick: changing file name, restricting to a smaller set of loop trip count tests